Comparison of Cherenkov excited fluorescence and phosphorescence molecular sensing from tissue with external beam irradiation
Comparison of Cherenkov excited fluorescence and phosphorescence molecular sensing from tissue with external beam irradiation
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DOI：
10.1088/0031-9155/61/10/3955
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发表时间：
2016-05-21
影响因子：
3.5
通讯作者：
Pogue, Brian W.
中科院分区：
文献类型：
--
作者：
Lin, Huiyun;Zhang, Rongxiao;Pogue, Brian W.
医用直线加速器(LINAC)提供的电离辐射在治疗组织内产生切伦科夫辐射。这种光的一部分，在600-900 nm波长范围内，通过厘米长的组织传播，可用于激发体内的光学探针，使组织分析物的分子传感成为可能。将发射信号从切伦科夫激发背景中分离出来的成功与否取决于关键因素，例如：(I)探测光谱的斯托克斯位移；(Ii)激发态寿命；(Iii)探测浓度；(Iv)组织表面下的深度；以及(V)使用的辐射剂量。以前的研究只专注于磷光染料的成像，而不是荧光染料。然而，生物上重要的磷光染料只有几种，而相比之下，与生物相关的荧光染料有数千种。因此，本研究的重点是使用商用近红外荧光探针IRDye 680RD、IRDye 700DX和IRDye 800CW来研究切伦科夫激发发光的有效性，并将它们与特性良好的氧敏染料氧膦PtG4磷光探针进行比较。每个探头由6 mV外辐射束的切伦科夫光激发，并以连续波或时间门控模式进行测量。检测是通过对发光信号进行光谱分解，并在ICCD探测器上以光谱仪为基础的分离来测量的。结果表明，IRDye 700DX和PtG4具有最大的信噪比。在磷光探头PtG4的情况下，由于发射在微秒(穆S)时间尺度上衰减，可以进行时间门控采集，并且在探头浓度和探测深度方面允许更高的效率。在5 mm深度包含探针的模体可以在纳摩尔范围内的浓度下被检测到，并且在接近3厘米的组织模拟模体中的深度可以被检测到。体内研究表明，在辐射剂量低于5cGy时，很容易检测到5nmoL的染料。由于浓度、辐射剂量和深度都对检测到的信号的电平有影响，因此有可能以牺牲其他参数为代价来改善这些参数中的任何一个。这种光学记者体内纳摩尔敏感性的范例引入了在治疗过程中或在诊断时使用生物相关浓度的荧光记者进行肿瘤分子传感的概念。
Ionizing radiation delivered by a medical linear accelerator (LINAC) generates Cherenkov emission within the treated tissue. A fraction of this light, in the 600-900 nm wavelength region, propagates through centimeters of tissue and can be used to excite optical probes in vivo, enabling molecular sensing of tissue analytes. The success of isolating the emission signal from this Cherenkov excitation background is dependent on key factors such as: (i) the Stokes shift of the probe spectra; (ii) the excited state lifetime; (iii) the probe concentration; (iv) the depth below the tissue surface; and (v) the radiation dose used. Previous studies have exclusively focused on imaging phosphorescent dyes, rather than fluorescent dyes. However there are only a few biologically important phosphorescent dyes and yet in comparison there are thousands of biologically relevant fluorescent dyes. So in this study the focus was a study of efficacy of Cherenkov-excited luminescence using fluorescent commercial near-infrared probes, IRDye 680RD, IRDye 700DX, and IRDye 800CW, and comparing them to the well characterized phosphorescent probe Oxyphor PtG4, an oxygen sensitive dye. Each probe was excited by Cherenkov light from a 6 MV external radiation beam, and measured in continuous wave or time-gated modes. The detection was performed by spectrally resolving the luminescence signals, and measuring them with spectrometer-based separation on an ICCD detector. The results demonstrate that IRDye 700DX and PtG4 allowed for the maximal signal to noise ratio. In the case of the phosphorescent probe, PtG4, with emission decays on the microsecond (mu s) time scale, time-gated acquisition was possible, and it allowed for higher efficacy in terms of the probe concentration and detection depth. Phantoms containing the probe at 5 mm depth could be detected at concentrations down to the nanoMolar range, and at depths into the tissue simulating phantom near 3 cm. In vivo studies showed that 5 nmol of dye was readily detected with radiation doses less than 5 cGy. Since concentration, radiation dose and depth each contribute to the level of the detected signal, it may be possible to improve any of these parameters at expense of the others. This paradigm of nanoMolar sensitivity for optical reporters in vivo introduces the concept of molecular sensing of tumors during therapy or diagnostically with biologically relevant concentrations of fluorescent reporters.